Thermal responsive system



Aug 16, 1949- G. cAMlLLl ET AL l 2,479,307

THERMAL RESPONS IVE SYSTEM Filed April 4, 1946 I rwvev'wtofs: Gmielmo Cml Il', James [vlc: Kerw'rwey,

by Thai? Attorney Patented Aug. 16, 1949 2,479,307 THERMAL RESPONSIVE SYSTEM Guglielmo Camilll and James F. McKenney, Plttseld, Mass., assignors to General Electric Company, a corporation of New Application April 4, 1946, Serial No.

York

1 Claim. (Cl. 297-5) This invention relates to thermalL responsive systems and more particularly to improvements in thermal relays and temperature indicators for electric induction apparatus.

The commonest example of an electric induction apparatus is a transformer. formers are usually mounted in a steel case which as a cooling medium. It is very often desirable and even necessary to indicate the internal temperature of the apparatus. In addition, it is often necessary to have automatic means, such as lay, which will tripping a circuit breaker so as to de-energize the transformer in case it becomes overheated.

sure throughout the entire system is therefore the vapor pressure in the top of the bulb and this pressure is almost entirely proportional to the temperature of the bulb.

The bellows or the apparatus actuated thereby must be carefully calibrated in order that a correct indication or response will be given by the n additional object of vide a new and improved the invention is to protemperature indicating and control device suitable for use with power transformers.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claim.

Referring now to the single figure of the accomprising a transformer tank I which is substantially illled with liquid 2 of any suitable type. The

surface of the liquid is a. closed bulb 3 to which is sealed a capillary tube I which enters through the top of the bulb and extends to near the bottom'. The capillary tube connects with a sealed element or casing 5 having a bellows 6` or other equivalent The gauge or relay end of the system comprises casing I0 in which is mounted a chamber II having a diaphragm or bellows I 2 or its equivalent which is provided with a movable wall I3 to which is attached a plunger I4, the end of which connects to a. chamber I9 including a bellows or diaphragm 20 having a movable member 2I which operates a lever 22 against the opposing force of a biasing spring 23 so as to actuate any suitable device, such as a micro switch or switchette 24.

The inside of the chamber I I and of the piping I1 and of the gauge I8 and the chamber I9 are completely filled with liquid 25, there being no vapor in this part of the system. Good results have been obtained with turpentine.

In the operation of the system shown in Fig. 1 changes in temperature of the liquid 2 in the main transformer tank I will vary the pressure of the vapor in the bulb 3 and this pressure will be transmitted throughout the entire system and through the abutting plungers 8 and I4 to the gauge I8 and the switch 24.

By reason of what may be described as the dry connection between the meter case I and the rest of the system, which connection consists merely of the abutting or mechanical engagement of the plungers 8 and IIand the similar engagement of the flanges I and I6, any failure of the apparatus in the relay case I9 will not affect the sealed vapor pressure system which includes the bulb 3 and the bellows 6. Consequently, the relay case can be removed and be replaced by a duplicate very simply and easily.

Furthermore, it is not necessary that the different relay units or cases be exact duplicates, that is to say, the physical relationship between the end of thevplunger I4 and the face of the ilange I6 is not critical. This is because the pressure throughout the entire system is determined entirely by the vapor pressure of the liquid 9 in the bulb 3 so that substantial variations in length of the plunger I4 in different relay units will merely cause slight compression or expansion of the vapor in the bellows 9, but as the pressure of the vapor is entirely a function of its temperature and not of its volume, it will be seen that the system is self-compensating. It is therefore only necessary to calibrate each relay unit so that its device I8 will'indicate correctly the pressure of the liquid 25 and so that its switch 24 will be operated at the same value of pressure of the liquid25. This latter is controlled by an adjusting screw 26 for varying the force of the spring 23.

While there has been shown and described a particular embodiment of this invention, it will be obvious to those skilled in theart that various changes and modications can be made therein without departing from the invention and, therefore, it is aimed in the appended claim to cover all such changes and modiilcations as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

In combination, a closed tank for electrical apparatus having a temperature to be responded to, a sealed vapor pressure system having a bulb located in said tank so that its temperature has a predetermined relation to sald temperature to be responded to, a hollow expansive and contractive element having a movable wall accessible from outside said tank, a capillary tube interconnecting the bottom of said bulb and the interior of said expansive and contractive element, a liquid lling all of said system except the top part of said bulb which is lled with the vapor of said liquid whereby the pressure in said system is the vapor pressure of said liquid, a liquid pressure system wholly outside'said tank having a hollow expandable and contractable member with a movable wall in effective contact with the wall of said expansive and contractive element which is accessible from outside said tank, a second hollow expandable and contractable member having a movable wall for actuating a responsive element, a conduit interconnecting snid expandable and contractable elements, a liquid entirely llling said second system, a main spring for determining the liquid pressure at which said second hollow expandable and contractable member actuates said responsive element connected to the movable wall of said second expandable and contractable member, and a liquid pressure responsive device connected to said conduit, said device having a movable pointer whose position is directly proportional to the pressure of said liquid.

GUGLIELMO CAMILLI. JAMES F. MCKENNEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,300,717 Fulton Apr. l5, 1919 1,413,073 Thelen Apr. 18, 1922 1,523,950 Fulton Jan. 20, 1925 1,593,170 Giesler July 20, 1926 2,214,236 Seldon Sept. 10, 1940 2,214,298 Gilbert Sept. 10, 1940 2,221,347 Giesler Nov. 12, 1940 2,274,254 Newton Feb. 24, 1942 

